1. Field of the Invention
The present invention pertains to energy connectors and more particularly to connectors for high pressure environments.
2. Related Prior Art
Tools used in drilling, logging, and producing oil wells commonly consist of various electronic instruments and circuits contained at atmospheric pressure within one or more pressure housings in the downhole tools. The surrounding downhole environment may exhibit pressures up to 30,000 psi at temperatures up to 500 F. The electronics inside the pressure housings require a hermetic type electrical connector that interconnects the electrical circuits in the separate housings and/or with electrical conductors in a wireline to maintain communications with electronic instruments at the surface. The connectors must easily connect and disconnect and function as electrical conductors in extreme hostile liquid environments such as brine, oil base drilling mud and fluids that may contain hydrogen sulfide, carbon dioxide, methane, and other elements at the extreme downhole ambient conditions. The connectors may carry substantial amounts of power with signals of several hundred volts being common.
A typical single pin type connector to which aspects of the invention pertain includes a conductive pin surrounded by an insulating material which in turn is encased in a metal body. Two types of construction are generally used. In one type, the center pin is insulated and bonded in place with the outer metal body by a fused glass insert located at some distance from each end of the metal body. A ceramic insulator is then inserted in the ends and bonded in place with an epoxy adhesive. The fused glass functions both as an insulator and as a hermetic seal. In another type of construction, the center pin is insulated from the outer metal body by a one piece ceramic insulator that is bonded to the pin and metal body with a metallic brazing material. In this case, the ceramic material functions as the insulator and the braze functions as the hermetic seal. This device generally represents the prior art devices now in use. Examples of such connectors are included in U.S. Pat. Nos. 3,793,608 and 3,898,731, each of which is incorporated herein by reference. Commercial connectors of this type are available from Kemlon Products, Pearland, Tex. A plastic bodied connector of somewhat similar construction is described in U.S. Pat. No. 5,203,723, which is incorporated herein by reference.
An outline of a typical connector as described above is shown in FIG. 1, where connector 4 has a conductor pin 2 that extends through connector body 1 and is internally configured and sealed as described above. Connector 4 is commonly screwed into a closely dimensioned port in bulkhead 7 (see FIG. 2) such that elastomer o-ring 8 in groove 3 is compressed between the groove 3 and an inner diameter surface 11 of the port to prevent the passage of high pressure fluid 10 past o-ring seal 8 and contaminate the interior atmospheric pressure area 15. As is common in high pressure applications, back-up ring 9 may be inserted in the groove to prevent the extrusion of elastomer o-ring 8 into the gap between housing 1 and surface 11. The effectiveness of back-up rings at high pressures and temperatures is critical to the proper operation of this type of sealing configuration. Back up ring 9 is commonly spirally cut, also called a scarf cut, such that it may be collapsed to the outer diameter of groove 3 during installation. Then, high pressure fluid 10 acting on o-ring 8 is used to force back-up ring 9 to extend out past the edge of groove 3 to contact surface 11 and prevent extrusion of o-ring 8. At high pressure, it is common for o-ring 8 to exert a large axial force on back-up ring 9 such that the friction between back-up ring 9 and the wall of groove 3 is too great to allow sufficient movement of back-up ring 9 to close the gap between the connector and surface 11. This leads to extrusion of o-ring 8 and commonly failure of the seal. This allows downhole fluid 10 to penetrate the atmospheric area 15 with catastrophic consequences. It is also common for personnel to install the back-up rings on the wrong side of the o-ring such that there is no tendency for the back-up ring to be properly actuated.
There is a demonstrated need for a highly reliable connector seal for high pressure high temperature environments. The present invention addresses these and other shortcomings of the prior art described above.